Does Vitamin D Deficiency Epidemic Parallel with Allergy and Asthma Epidemic?

Vitamin D (VD) deficiency has re-emerged, after more than hundred years, as a public health problem worldwide. Asthma and allergic disorders constitute another major public health problem with studies having recorded increasing prevalences worldwide since the decade of the 60s. Most of the available experimental and epidemiologic evidence point towards a causal association between low levels of VD and the development of asthma and allergic disorders, and imply a role of VD deficiency on the currently high prevalences of asthma and allergic diseases. The proposed, but still largely hypothetical, underlying mechanism is that VD affects the programming of the fetus and it also has a central modulating role in immune functions involved in asthma and allergic disorders. However, the evidence is not yet clear, since there are studies which support that VD supplementation during pregnancy may promote the development of asthma and allergic disorders. More researches, and especially randomized clinical trials, are required in order to draw safe conclusions and define the role of VD in the prevention or even therapy of asthma and allergic disorders.